Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07J—STEROIDS
  • C07J71/00—Steroids in which the cyclopenta(a)hydrophenanthrene skeleton is condensed with a heterocyclic ring
  • C07J71/0005—Oxygen-containing hetero ring
  • C07J71/0026—Oxygen-containing hetero ring cyclic ketals
  • C07J71/0031—Oxygen-containing hetero ring cyclic ketals at positions 16, 17

Definitions

• the present invention concerns a process for the preparation of 16,17 acetals of pregnane derivatives starting from the corresponding 16,17-acetonides.
• the process of the invention is conveniently applicable to the synthesis of 16 ⁇ ,17 ⁇ -butylidendioxy-11 ⁇ ,21-dihydroxypregna-1,4-diene-3,20-dione, described in US Patent No. 3,929,768 and GB Patent No. 1,429,922, a useful compound in human therapy, known also as budesonide, and to the synthesis of similar compounds.
• the invention refers moreover to new 16,17 acetals of pregnane derivatives, obtained according to said process.
• said acetals exist as couples of epimers which can be separated with difficulty by means of cumbersome techniques which are difficult to be applied industrially, such as column chromatography, HPLC (high performance liquid chromatography) or gel-filtration as described in GB Patent No. 1,428,416 and US Patent No. 3,928,326.
• column chromatography HPLC (high performance liquid chromatography) or gel-filtration as described in GB Patent No. 1,428,416 and US Patent No. 3,928,326.
• one of the two epimers hereinafter designated as "B" proved to be more active than the other one.
• the process according to the present invention allows to overcome the drawbacks of the prior art and consists in a direct transketalization reaction with aldehydes on 16,17-acetonides, in the presence of hydrohalogen acids.
• steroidal acetals or cyclic ketals can be hydrolized to diol compounds by treatment with aqueous HF or HCl, at temperatures ranging from -30° to +25°C (US Reissue No. 26877, 12-5-1970).
• the method of the invention occurs in almost quantitative yields and, even more surprisingly, the more active epimer is almost exclusively obtained.
• the steric selectivity can also be suitably controlled by changing the reaction conditions. Particularly, by changing the reaction temperature, it is possible to obtain products containing from 50% to more than 90% of the more active epimer (B epimer).
• Another aspect of the present invention is the transformation of the less active epimer of a 16,17-acetal of pregnane derivatives into the more active epimer.
• a further essential feature of the invention resides in the use, as starting materials, of 16,17- ketals, preferably 16,17-acetonides, which, differently from the 16,17-diol compounds up to now considered as the sole precursors for the preparation of the corresponding acetals, are stable, easily available compounds which can be easily purified.
• the acetonides for the above cited reasons, are often used for the purification of diols and can be therefore considered to be precursors of the latter, and not vice versa, having moreover a lower production cost.
• the process of the invention is particularly convenient, also leaving the exceptionally high yields obtained out of consideration, and it is possible to prepare new compounds previously impossible to be prepared because of the unavailability or the unstability of the corresponding diols.
• R 1 represents a C 1 -C 12 alkyl group
• new compounds according to the invention are:
• the 16,17-acetonides are reacted with aldehydes having formula R CHO, in molar ratios ranging from 1:1 to 1:5, preferably from 1:1 to 1:1.1, in aqueous hydrofluoric acid and concentrations ranging from 20 to 90%, preferably from 50 to 70%, at a temperature from -70 to 20°C, the temperature being choosen in order to give the desired epimer ratio.
• the product is isolated by simple water dilution, in high purity.
• hydrofluoric acid instead of hydrofluoric acid, it is possible to use hydrochloric acid. In this case, however, the reaction is less selective in the isomers ratio and the product obtained is less pure.
• the acetonide in the process of the invention, can be replaced by the corresponding diol derivative. Under these conditions the acetal is always produced with an excess of the B epimer, but with a lower selectivity.
• Another aspect of the invention concerns the conversion of the less active epimer of a 16,17-acetal into the more active epimer.
• a mixture of budesonide containing only 30% of the B epimer subjected to the above mentioned conditions for the preparation of budesonide from the corresponding acetonide, is transformed into budesonide having more than 90% of B epimer.
• This process is very useful to recover active product from the mother liquors (as deriving from the crystallization) enriched in A epimer.
• budesonide like compounds For the epimerization of budesonide like compounds it is sufficient the treatment with hydrofluoric acid alone but, usually, an amount (lower than the stoichiometric one) of the aldehyde (in the instance of budesonide, butyraldehyde) is added in order to avoid any formation of the 16,17-diol.
• a epimer or "B epimer” is made according to US patent No. 3,928,326 and the epimer ratio was determined by HPLC using a reversed phase RP-18 column, eluting with 40% acetonitrile.
• Example 2 The procedure described in Example 1 was repeated, except that the desonide was replaced by other acetonides. The corresponding acetals with butyraldehyde were obtained in almost quantitative yields and with the epimer ratios reported in the following Table.
• Example 2 The procedure described in Example 1, was repeated, except that the reaction was carried out at -78° (and quenching the reaction after 12 hours at this temperature).
• Budesonide was obtained (A/B ratio 47/53) together with unreacted desonide (about 40%).
• Example 1 The procedure described in Example 1 was repeated, substituting butyraldehyde by isobutyraldehyde. 16a-Hydroxyprednisolone 16,17-acetal, apparently only one epimer, was obtained.
• budesonide (A/B ratio 70/50) instead of desonide, budesonide having A/B ratio of 10/90 was obtained.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Steroid Compounds (AREA)
• Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Heterocyclic Carbon Compounds Containing A Hetero Ring Having Oxygen Or Sulfur (AREA)
• Investigating Or Analysing Biological Materials (AREA)
• Adhesives Or Adhesive Processes (AREA)
• Diaphragms For Electromechanical Transducers (AREA)
• Saccharide Compounds (AREA)

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Publications (3)

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Cited By (18)

Families Citing this family (37)

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• 1984
  • 1984-06-11 IT IT21343/84A patent/IT1196142B/it active
• 1985
  • 1985-05-24 ES ES543499A patent/ES8705462A1/es not_active Expired
  • 1985-05-24 FI FI852093A patent/FI81809C/fi not_active IP Right Cessation
  • 1985-05-28 AT AT85106522T patent/ATE56725T1/de not_active IP Right Cessation
  • 1985-05-28 DE DE8585106522T patent/DE3579750D1/de not_active Expired - Lifetime
  • 1985-05-28 EP EP85106522A patent/EP0164636B1/de not_active Expired - Lifetime
  • 1985-05-30 US US06/739,131 patent/US4695625A/en not_active Expired - Lifetime
  • 1985-05-30 DK DK243085A patent/DK163433C/da not_active IP Right Cessation
  • 1985-05-30 JP JP11762185A patent/JPS6140299A/ja active Granted
  • 1985-05-31 CA CA000482945A patent/CA1336513C/en not_active Expired - Lifetime
  • 1985-06-10 NO NO852327A patent/NO164905C/no unknown
• 1987
  • 1987-01-02 US US07/000,185 patent/US4835145A/en not_active Expired - Lifetime

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